In the field of hoppers for feeding crowns or caps for bottles, the apparatus most commonly used is shown in U.S. Pat. No. 1,932,529, Nagy; Oct. 31, 1933. Apparatus of this kind or variations thereof rely upon gravity and depend on the laws of probability to move crowns through the system. One of the main problems with the Nagy and similar hoppers is that they accept considerably more crowns than are fed out of the machine, and by doing so, the crowns are "churned;" that is, they are tumbled over and over. This leads to what is termed "dusting," which is the result of the lacquer coatings on the crowns becoming abraded by the sharp edges of the stamped crowns.
Many of the troubles or difficulties encountered in the lining of bottle caps or crowns stem from the malfunctions of the hopper. For example, if the hopper doesn't keep the turntable conveyor of the seal liner machine filled, the high-frequency generator which is used to preheat the crowns preliminary to depositing or metering the charges of plastic material into the crowns reacts due to a difference in coil loading. As a consequence, the crowns adjacent to the empty space on the conveyor are either over-heated or under-heated. When that occurs, pellets or charges of the plastic material may bounce out of the crowns or shift off center, and a whole chain of circumstances begin, the final result of which is the shutdown of the machine. Seal liner machines including a turntable conveyor to which hoppered crowns are fed and are heated while on the conveyor are disclosed in U.S. Pat. Nos. 3,135,019; June 2, 1964 and 3,360,827; Jan. 2, 1968, to Alchele.
The Nagy hopper was designed to feed 600 crowns per minute. Today, many crown producers have refined the machine and have achieved production of approximately 850 crowns per minute. Nevertheless, these refined machines, as well as the original Nagy machine have the limitations and disadvantages outlined above. The rate of operation of the seal liner machine described in the aforementioned Aichele, U.S. Pat. No. 3,360,827 has been limited by the rate of operation of hoppers available to feed crowns to the machine.
It has been proposed (French Patent No. 1,114,037; Dec. 12, 1955) to provide a hopper which includes a supply chute, a vibratory feeder, a rotatable bowl and a vertically arranged exit chute which receives objects from the bowl from an intermediate passage. Both the intermediate passage and the exit chute are of a dimension or width to receive a single line of articles or objects processed by the hopper. The exit chute has associated therewith two vertically spaced photoelectric cells. When the level of objects in the exit chute reaches the top cell, the vibratory feeder is stopped. When the light beam at the lower cell is free, the vibratory feeder is turned on.
This prior art hopper has the limitation that when the lower cell starts the vibratory feeder after the last object in the chute has passed, the first object from the newly fed objects will be unable to catch up with the last object, thereby leaving a gap in the objects being fed. As previously indicated, and particularly with reference to the lining of bottle caps or crowns, if the hopper does not keep the turntable conveyor on the seal liner machine filled, there are problems stemming from the high-frequency generator which is used to preheat the crowns. Actually, the prior art apparatus disclosed in the French patent does not include a reservoir which, as will hereinafter be explained, affords a continuous constant stream of crowns or other disk-like objects.